c# - C#中的多变量switch语句

Question

我想使用带有多个变量的 switch 语句，如下所示:

switch (intVal1, strVal2, boolVal3)
{
   case 1, "hello", false:
      break;
   case 2, "world", false:
      break;
   case 2, "hello", false:

   etc ....
}

有没有办法在 C# 中做这样的事情？ (出于显而易见的原因，我不想使用嵌套的 switch 语句)。

.net 开发团队通过实现这个功能回答了这个问题:Multi-variable switch statement in C#

Answer 1

是的。从 .NET 4.7 和 C# 8 开始支持它。语法几乎与您提到的一样，但带有一些括号(请参阅 tuple patterns)。

switch ((intVal1, strVal2, boolVal3))
{
    case (1, "hello", false):
        break;
    case (2, "world", false):
        break;
    case (2, "hello", false):
        break;
}

---

如果你想切换并返回一个值，有一个切换“表达式语法”。这是一个例子；注意在默认情况下使用 _:

string result = (intVal1, strVal2, boolVal3) switch
{
    (1, "hello", false) => "Combination1",
    (2, "world", false) => "Combination2",
    (2, "hello", false) => "Combination3",
    _ => "Default"
};

下面是上面链接的 MSDN 文章中的一个更具说明性的示例(剪刀石头布游戏):

public static string RockPaperScissors(string first, string second)
    => (first, second) switch
    {
        ("rock", "paper") => "rock is covered by paper. Paper wins.",
        ("rock", "scissors") => "rock breaks scissors. Rock wins.",
        ("paper", "rock") => "paper covers rock. Paper wins.",
        ("paper", "scissors") => "paper is cut by scissors. Scissors wins.",
        ("scissors", "rock") => "scissors is broken by rock. Rock wins.",
        ("scissors", "paper") => "scissors cuts paper. Scissors wins.",
        (_, _) => "tie"
    };